1. Field of the Invention
This invention relates broadly to the field of easy open liquid containers for beverages and the like. More specifically, it relates to an improved easy opening ecology can end mechanism that is advantageous in that it minimizes splashing of the beverage during opening of the can by a consumer.
2. Description of the Prior Art and Related Technology
An easy open end, for the purposes of this document, may be defined as a can end which is designed to be opened by a consumer without using a can opener or similar tool. A pour-type can end is defined as a can end of the type which defines a pour spout opening after it has been opened to enable the consumer to pour a beverage or other liquid from the can assembly in a controlled manner. An ecology type easy open can end is defined as one where the tab stays attached to the can after opening, to prevent littering.
Pour-type can ends typically include a displaceable end panel portion which, through force that is applied by pulling on a gripping-tab that is connected to the displaceable portion, is peeled back from the end panel along a score line to define the pouring spout. An example of a conventional pour-type can end is depicted in FIG. 1. A wall 10 of a can end is shown having a displaceable panel 12 defined therein by a score line 14. As shown in FIG. 1, the score line 14 comprises multiple portions, each of which has a different radius of curvature. The first portion 25 of the score line 14 extends from point 24, which is the point on the score line that is directly ahead of the rivet 20, to point 30. The second portion 31 of the score line 14, which is an intermediate portion, extends from point 30 to point 32. The third portion of the score line 14, which is the main portion 33, extends from point 32 to point 34, where the score line terminates. Thus, point 30 is the point on the score line 14 where the first portion 25 and the intermediate portion 31 of the score line intersect, while point 32 is the point where the intermediate portion 31 and the main portion 33 of the score line intersect. As also shown in FIG. 1, the first portion 25 of the score line 14 is substantially straight, having a radius of curvature of essentially infinity. The intermediate portion 31 has a first radius of curvature. The main portion 33 is formed from several sections having different radii of curvature. In any event, as shown in FIG. 1, the section of the main portion 33 adjacent intersection point 32 has a radius of curvature that is greater than the radius of curvature of the intermediate portion 31. As also shown in FIG. 1, the intermediate portion 31 of the score line 14 is preferably tangent to the first portion 25 and the main portion 33 at the intersection points 30 and 32, respectively. As is typical in this area of technology, a secondary antifracture score line 16 that is roughly parallel to score line 14 is provided on the displaceable panel 12 to reduce stress imposed on the score 14 during processing and handling. A tab 18 that is connected to wall 10 via a rivet 20 includes a forward facing tab nose 28 that is intended to apply a downward force to displaceable panel 12 at a pressure point 26 when a rearward facing heel 22 of the tab 18 is lifted, as may readily be envisioned by viewing FIG. 1. As the heel 22 continues to rise, it ruptures the score 14 at the point 24 that is directly ahead of the rivet 20. The score 14 then ruptures along its bottom as viewed in FIG. 1, along portion 25 to the intersection point 30 of the radiused lower left portion of the score 14.
As force is applied increasingly at the pressure point 26 by the tab nose 28, the score begins to separate along the radiused curve at the lower left in FIG. 1, that is from the first intersection point 30 to the second intersection point 32. As may be seen in FIG. 1, the pressure point 26 is positioned forwardly (i.e., in the direction of a center line 38 of the tab 18 as shown in FIG. 1) of the second intersection point 32 by a distance D.sub.1, which in one sample known to the inventor has a value of 0.0287 inches. In addition, the pressure point 26 is positioned to the right of the second intersection point 32 (i.e. along an axis that is perpendicular to the center line 38) by a distance D.sub.2, which in the sample referred to above is about 0.1172 inches or greater. These distances are large enough that a buildup of significant force is required at the pressure point 26 in order to advance separation of the score 14 beyond the second intersection point 32. When this separation does occur, it does so with a release of force that is large enough that the score 14 will separate nearly instantaneously all the way about the forward portion of the panel 12 to the final transition point 34. As it separates, the panel 12 folds downwardly about a fold line 36 into the interior of the can body. The plane along which the panel 12 moves is indicated by reference numeral 40 in FIG. 1, and this plane is positioned at an angle .alpha. with respect to the centerline 38, which is in the sample referred to above about 18.2 degrees. If the panel 12 folds downwardly to a 90 degree angle, it will extend into the interior of the can body by a distance D.sub.3.
When a can body is filled with a soft drink or other liquid, a head space of air is typically left at the top of the can body before the can end is installed. In more modern plastic containers, the head space must be minimized. When a can end such as that described above with reference to FIG. 1 is used on a can that has minimal head space, the near instantaneous separation of the score 14 described above results in the panel 12 snapping forcefully down into the beverage, which can cause the beverage to splash. Obviously, this is a problem that needs to be addressed.
It is clear that a need exists for an improved easy open mechanism for a can end that is attractive and convenient for the consumer to use, and that minimizes the potential for splashing during opening, yet maintains sufficient strength and integrity for processing and shipping.